The use of Petri dishes for growing colonies of microorganisms such as bacteria or fungi is well known. A Petri dish typically comprises an open dish for holding microorganism growth medium and an overlapping cover that isolates the growth medium and microorganisms from the external environment. A so-called mono plate is a slightly smaller version of a Petri dish that is used in large numbers in non-clinical settings such as food and pharma manufacturing, biotech labs and water testing.
Petri dish covers may be loosely fitting so that the seal on the dish arises simply from the weight of the cover bearing upon the cylindrical side walls of the dish. Petri dish covers may also be tightly securable to and detachable from the dish, which prevents opening of the Petri dish when it is accidentally bumped or knocked over. One such Petri dish design is disclosed in U.S. Pat. Nos. 3,769,936 and 5,854,065 wherein the cover may be secured to the dish by ribs or lugs in the side walls of the cover that resiliently contact the side walls of the dish so as to form a compression fit. However, this design has the inherent drawback that the compression fit is often either too tight to allow ready disengagement between the cover and dish or too loose, which can lead to accidental spillage or contamination when handling the Petri dish.
Mono plates are typically fabricated from polymeric material in mass quantities at a sufficiently low cost as to be disposable after a single use. The dish portion of the mono plate is pre-loaded with growth medium under sterile conditions and packaged for shipment to the end user.
There is an ongoing need in the art for a lockable cell growth chamber that does not lock except upon application of a specific intentionally applied force, and that, once locked, provides a locking engagement between the cover and the dish, and which may be readily disengaged from the locking engagement. These needs are met by the present invention, which is summarized and described in detail below.